Issued  February  7,  1912. 


U.  S.  DEPARTMENT   OF    AGRICULTURE, 

OFFICE  OF  PUBLIC   ROADS— Circular  No.  97. 
LOGAN  WALLER  PAGE,  Director. 


COKE -0 YEN  TARS  0E  THE 
UNITED  STATES. 


BY 


PRfiVOST    HUBBARD, 

Chemist,  Office  of  Public  Roads. 


h    rSpVlCK! 


LETTER  OF  TRANSMITTAL 


United  States  Department  of  Agriculture, 

Office  of  Public  Roads, 
Washington,  D.  C,  October  19,  1911. 
Sir:  I  have  the  honor  to  transmit  herewith  the  manuscript  of  a 
circular  by  Mr.   Prevost  Hubbard,   chemist  in  this  office,   entitled 
"Coke-Oven  Tars  of  the  United  States."     This  publication  gives  the 
results  of  examinations  of  all  the  coke-oven  tars  at  present  manu- 
factured in  this  country,  together  with  a  brief  discussion  of  their 
properties  in  relation  to  their  use  as  road  materials.     I  respectfully 
request  that  this  manuscript  be  published  as  Circular  97  of  this  office. 
Respectfully, 

Logan  Waller  Page, 

Director. 
Hon.  James  Wilson, 

Secretary  of  Agriculture. 


URL  Un    ' 


COKE-OYEX  TARS  OF  THE  UNITED  STATES. 


The  rapidly  increasing  use  in  this  country  of  refined  coal  tar  in  the 
treatment  and  const  miction  of  roads  and  the  fact  that  an  immense 
quantity  of  coal  tar  will  ultimately  become  available  for  this  purpose 
through  the  installation  of  by-product  coke  ovens  make  it  highly 
desirable  to  obtain  accurate  information  as  to  the  properties  of  coke- 
oven  tars  which  are  being  produced  at  present.  Attention  was 
called  by  the  author  to  the  importance  of  this  subject  in  a  recent 
publication,1  as  follows: 

While,  in  the  manufacture  of  con]  gas.  the  production  of  tar  is 
absolutely  unavoidable,  this  is  not  true  of  the  manufacture  of  coke 
for  metallurgical  purposes.  There  are  two  general  types  of  coke 
ovens  in  use  at  present,  in  one  of  which  no  attempt  is  made  to  recover 
the  volatile  products  of  the  coal.  This  is  the  oldest  form  of  oven, 
known  as  the  "beehive,"  and  is  extensively  used  in  this  country 
to-day.  Tt  is  constructed  of  brick  and  as  its  name  implies  has  the 
form  of  a  beehive.  Bituminous  coal  is  placed  in  this  oven  or  kiln 
and  a  part  of  it  burned  in  order  to  carbonize  the  remainder,  while  the 
volatile  products,  such  as  gas.  ammonia,  and  tar,  are  allowed  to  escape 
through  an  opening  in  the  top  of  the  kiln,  where  they  are  lost  in  flame 
and  smoke. 

Coke  ovens  in  which  the  by-products  are  saved  are  now  used  to 
some  extent  in  this  country,  and  sooner  or  later  will  undoubtedly 
replace  the  old-style  oven  entirely,  and  thus  increase  our  output  of 
tar  enormously.  The  reason  that  they  have  not  been  more  generally 
adopted  in  tlii-  country  is  that  in  the  United  States  tars  are  of  much 
less  economic  importance  than  in  the  European  countries,  where 
great  chemical  industries  are  based  upon  the  utilization  of  this 
material.  <  rermany  in  particular  is  far  in  advance  of  us  in  this  Held 
and  exports  to  this  country  alone  coal-tar  products  to  the  value  of 
•  ral  million  dollars  each  year.  With  the  development  of  the 
road-tar  industry,  which  promises  to  consume  vast  quantities  of  tar, 
and  the  aecessity  for  refining  such  tars  before  use,  the  general  adoption 
of  by-product  ovens  is  only  a  matter  of  time.  What  this  will  mean 
in  the  increase  in  tar  production  can  be  imagined  from  the  fact  that  in 
1908,  oiii  of  b  total  of  over  26,000,000  t<>ns  of  coke  produced  in  coke 
oven-,  only  a  little  over  1,000,000  tons  were  obtained  from  by-product 

1 1  M0,  New  Vol 

:i 


4  COKE-OVEN    TARS   OF    THE   UNTTED   STATES. 

ovens.  About  22,000,000  Ions  of  coke  were,  therefore,  produced 
without  recovery  of  the  tar.  As  the  average  yield  of  coke  per  ton  of 
coal  was  66  per  cent,  this  would  represent  the  consumption  of  over 
33,000,000  tons  of  coal.  Upon  the  basis  of  a  yield  of  10  gallons  of 
tar  per  ton  of  coal,  it  may  be  seen  that  over  330,000,000  gallons  of 
tar  were  lost  in  1908  which  might  have  been  saved.  As  the  actual 
production  of  coal  tar  both  from  coke  ovens  and  gas  houses  amounted 
to  about  101,000,000  gallons,  it  is  evident  that  over  three-fourths  of 
our  possible  production  of  tar  as  a  by-product  was  lost  during  that 
year.  At  a  valuation  of  2>s  cents  per  gallon,  this  means  a  loss  of  over 
$8,000,000.  With  such  an  increase  in  production,  however,  the 
monetary  value  of  coal  tar  would  have  dropped,  so  that  this  figure 
may  be  somewhat  exaggerated.  In  any  event,  at  a  conservative 
estimate,  the  tar  lost  each  year  from  nonrecovery  coke  ovens  is 
sufficient  to  build  9,000  miles  of  tar  macadam  road  15  feet  wide. 

This  estimate  was  based  on  data  taken  from  reports  of  the  United 
States  Geological  Survey.  In  a  later  report  by  Parker,1  it  is  shown 
that  over  53,000,000  tons  of  coal  were  consumed  in  beehive  ovens  in 
1910,  so  that  on  the  same  basis  it  would  appear  that  over  530,000,000 
gallons  of  tar  were  lost  during  that  year.  The  output  of  tar  from  by- 
product coke  ovens,  however,  has  also  continued  to  increase,  as 
shown  by  the  following  figures  taken  from  this  report: 

Tar  obtained  from  by-product  coke  ovens. 

Gallons. 

1908 42, 720,  609 

1909 60, 126, 006 

1910 66,  303,  214 

The  tar  thus  produced  in  1910  was  valued  at  $1,599,453,  or  about 
2.4  cents  per  gallon.  It  is  evident,  therefore,  that  the  value  of  the 
tar  lost  during  that  year  by  the  use  of  beehive  ovens  amounted  to 
approximately  $12,000,000.  That  the  use  of  by-product  ovens  is 
increasing  in  greater  proportion  than  the  use  of  the  beehive  oven  is 
shown  by  the  fact  that  for  the  former  type  the  increase  in  1910  over 
1909  in  tons  of  coke  produced  was  14.13  per  cent,  while  the  production 
from  beehive  ovens  increased  by  only  4.57  per  cent.  Parker  adds, 
however: 

While  noteworthy  progress  has  been  made  in  the  substitution  of  modern  retort-oven 
practice  for  the  wasteful  and  what  should  be  obsolete  beehive  or  partial-combustion 
method  of  coke  making  in  the  United  States,  this  country  is  still  much  behind  European 
countries  in  this  regard. 

He  says  further: 

The  yield  of  coal  in  coke  in  retort  ovens  exceeds  that  obtained  in  beehive  or  other 
partial-combustion  ovens  by  about  15  per  cent,  and  generally  the  quality  of  the  coke 
is  improved. 

i  The  Manufacture  of  Coke  in  1910,  United  States  Geological  Survey. 


COKE-OVEN    TABS    OF    THE    UNITED   STATES.  0 

In  order  to  determine  the  character  of  coke-oven  tars  at  present 
being  produced  in  the  United  States,  it  was  first  necessary  to  obtain 
samples  from  all  of  the  known  plants,  and  for  tins  purpose  reference 
was  made  to  a  list  of  by-product  and  retort  coke-oven  plants  of  the 
United  States  and  Canada  (Jan.  1,  1910),  winch  was  kindly  loaned  to 
the  author  by  Mr.  Parker  in  advance  of  its  publication.1  Letters 
were  then  written  to  each  plant  asking  for  the  following  information: 

(1)  a.  At  what  maximum  temperature  are  your  retorts  fired  in  your ovens? 

In  your ovens? 

b.  What  is  the  maximum  temperature  to  which  the  charge  of  coal  is  brought  in  your 
ovens?     In  your ovens? 

(2)  What  is  the  specific  gravity  of  your  crude  tar  in  your     ovens'.'     In  your 

ovens? 

(3)  What  percentage  of  free  carbon  is  found  in  your  crude  tar  from  your ovens? 

From  your ovens? 

Will  you  furnish  us  for  examination  a   L-gallon  sample  of  your  crude  tar  from 
your ovens'.'     From  your ovens?     To  be  sent  at  our  expense. 

Very  courteous  replies  were  received  from  the  manufacturers,  and  in 
practically  every  ease  samples  of  tar  were  also  forwarded.  The  blanks 
in  these  questions  were  Idled  out  by  inserting  the  names  of  the  type  or 
tvpes  of  ovens  operated  by  the  manufacturer  to  whom  they  were  sent. 
It  was  found  that,  where  two  types  of  ovens  were  operated  at  the  same 
plant,  no  attempt  was  made  to  separate  the  tar,  and  the  entire  output 
was  run  into  a  common  well.  In  such  cases  the  sample  of  tar  sub- 
mitted was  a  mixture  obtained  from  both  ovens.  The  report  of  these 
samples  i-,  given  at  the  bottom  of  Table  1. 

The  questions  concerning  temperature  were  asked  because  criticism 
from  an  authoritative  source  had  been  received  with  regard  to  a  state- 
ment made  by  the  author  in  a  former  publication'-'  to  the  effect  that 
in  the  production  of  tar  from  b>y-produc1  coke  ovens  " carbonization  is 
conducted  at  a  lower  temperature  than  in  tin  manufacture  of  coal  gas. 
The  resulting  tar,  therefore,  contains  a  smaller  amount  of  free  carbon, 
averaging  from  3  to  10  per  cent  *  *  *."  But  little  reliable  infor- 
mation on  this  subject  could  be  obtained  from  published  literature, 
although  the  opinion  seemed  to  prevail  that  carbonization  in  by- 
product coke  ovens  is  conducted  at  a  lower  t einperat  ure  than  in  mod- 
ern gas-house  practice.  Thus,  according  to  Lunge,1  "  Ililgenstock 
(J.  Gasbeleucht.,  1902,  617)  attributes  the  notorious  difference  be- 
t  ween  gas-tar  and  coke-oven  t  ar  wii  h  respeel  of  t  heir  contents  of  free 
carbon  and  other  products  of  pyrogenetic  decomposition  to  the  fact 

that    in  coke  ovens  the  escaping   vapors  do  not  attain   temperatures 

above  600°( '..  and  t  hat  t  hey  are,  moreover,  protected  againsl  decompo- 
sition by  the  dilution  of  the  heavj  vapors,  slowly  given  off  from  the 

i  Mineral  Rcaoam  of  the  United  -'.'•  ,  1909,  Part  n,  pp.  240-242,  Unit  Oeologioal  Survey. 

i  CtmdtfM,  Office  oi  Public  Road  ,  U.  8.  Department  ol  Agriculture,  | 

■  o  >i  T  ■•  in  i  v  tnmonJ  i,  Itb  ed.,  pari  I,  p.  28,  \  an  Noatrand. 


6 


COKE-OVEN    TARS    OF    THE   UNITED   STATES. 

Table  I. — Analyses  of  crude  coke-oven  tors 


General  information. 


Answers  to  questions. 


Sum  I 
No.   , 


I  ompany  and  location. 


Type  of 
oven. 


Maximum 

temperature 
of  firing 
retorts. 


Maximum 
tempera- 
ture to 
which  coal 
is  brought. 


Specific 

gravity 

of  crude 

tar. 


Per  cent 
of  free 
carbon 
in  tar. 


5126 
5123 
5124 

5137 
5121 

5125 

5128 
5200 

51 89 

51*30 


5081 
5095 

5083 
5159 

5107 
5086 
5078 
5087 

5109 


5188 
5404 


5108 


Solvay  Process  Co.,  Syracuse,  N.  Y.. 

Semet-Solvay     Co.,     Pennsylvania 

Steel  Co.,  Steelton,  Pa. 
Semet-Solvay  Co.,  National   Tube 

Co.,  Benwood,  W.  Va. 
Semet-Solvay  Co.,  Milwaukee  Coke 

&  Gas  Co. ,  Mil  waukee ,  W  is. 
Semet-Solvay    Co.,    Pennsylvania 

Steel  Co.,  Lebanon,  Pa. 
By-Prod  ucts      Coke      Corporation, 

South  Chicago,  111. 

Semet-Solvay  Co.,  Detroit,  Mich 

Semet-Solvey  Co.,  Empire  Coke  Co., 

Geneva,  N.  Y. 
Semet-Solvay  Co.,  Dunbar  Furnace 

Co.,  Dunbar,  Pa. 
Semet-Solvay  Co.,  Central  Iron   & 

Coal  Co.,  Tuscaloosa,  Ala. 
I  Philadelphia  Suburban  Gas  &  Elec- 
\\    trie  Co.,  Chester,  Pa. 

j  Semet-Solvay  Co.,  Ensley,  Ala 

The  New  England  Gas  &  Coke  Co., 
Everett,  Mass. 
A  Lackawanna  Steel  Co. ,  Lackawanna 
\    Iron  &  Steel  Co.,  Lebanon,  Pa. 

Dominion  Tar  &  Chemical  Co.,  Syd- 
ney, Nova  Scotia. 
,/ Hamilton  Otto  Coke  Co.,  Hamilton, 
\  Ohio. 

i  Carnegie  Steel  Co. ,  South  Sharon,  Pa 
;  I  Maryland  Steel  Co.,  Sparrows  Point, 
\    Md. 

Citizens'  Gas  Co.,  Indianapolis,  Ind. 

(Pittsburg  Gas  &  Coke  Co.,  The 
United  Coke  &  Gas  Co.,  Glassport, 
Pa. 

Zenith  Furnace  Co.,  Duluth,  Minn 


Semet-Sol- 
vay. 
do 

....do 

....do 

....do 

do 

do 

do 

do 

do 

L...do 


....do 

Otto  Hoff- 
man. 

|....do 

...do 

....do 

[United. 
[    Otto. 

do.... 

...do.... 


1050-1450°  C. 
1050-1450°  C. 
1050-1450°  C. 
1050-1450°  C. 
1050-1450°  C. 

1050-1450°  C 

1050-1450°  C 
1050-1450°  C. 

1050-1450°  C 

1250°  C 


1050°  C. 


1250°  C. 
i  1100°  C. 


11000°  C 

[(1800°  F.).. 
(2) 


(1111°  c... 
\(2000°  F.)... 

(1666°  C 

\(3000°  F.).. 

(1333°  C 

V2400°  F.)  . 

11222°  C 

\(2200°F.).. 


Illinois  Steel  Co. ,  Joliet ,  111 . 


Camden  Coke  Co.,  Camden,  X.  J. 


...do 

....do.... 

Koppers  . 
• do 


(Illinois  Steel  Co. ,  Indiana  Steel  Co. 
\    Gary,  Ind. 

I  Otto  Hoff- 
man. 
United 
Otto. 
(OttoHoff- 
j     man.. 
(United 
1 1    Otto. 
'(United 

Lackawanna  Steel  Co. ,  Buffalo,  N.  Y .  \      °tt0- 

iRothberg . 


Cambria  Steel  Co.,  Johnstown,  Va 


(-) 

(1222-1277°  C, 
«200  -  2300° 
■I     (F.) 

11444°  C 

\(2800°F.).. 

1100°  C 


950-1150°C. 
950-11.50°  C 
950-1150°  C 
950-1150° C 
950-1150°  C. 

950-1150°  C 

950-1150°  C 
950-1150°  C. 

950-1150  C°. 

1150°  C.... 

1000°  C... 

1150°  a... 

1 1200°  C . . . 

1000°  a... 

(1800°  F.). 

(2) 
mi0  a... 

(2000°  P.). 

1444°  C... 
(2600°  F.). 
1222°  a... 
(2200°  P.). 
1222°  C. . . . 
(2200°  F.). 

(2) 


12-1. 21 
12-1.21 
12-1.21 
12-1.21 
, 12-1. 21 


1.12-1.21 


(1000°  C 

\(1800°F.).. 

(1222°  C 

1(2200°  F.)... 

(1111°  C 

\(2000°  F.)... 
(1111°  c. 


|\(2000°  F.).. 

'fiooo0  a 


{(1800°  F.) 
|(1000°  c... 
\(1800°  F.) 


J    (2) 

1388°  a... 

i  (2500°  F.). 
i (880  -  950° 

I  c. 

833°  C 

(1500°  F.). 
1055°  C. . . . 
(1900°  F.). 
i  1111°  C  .. 
(2000°  F.). 
i  1111°C... 
(2000°  F.). 
1000°  C... 
(1800°  F.) 
1000°  C... 
(1800°  F.) 


i.  12-1. 21 
1.12-1.21 

L.  12-1.  21 

1.17 

1.161 

(20°  C  ) 

1.17 

(15°  C.) 
1.17 

1.10 
1.170 


1.2 

3  1.19 

Vl.  14-1.  IS 

(  (50°  F.I 
\        1.207 
10°  C 

(2) 


<  1.174 
1.169 


1.20-1.30 
5  (1.221) 


3-12 
3-12 
3-12 
3-12 
3-12 

3-12 

3-12 
3-12 

3-12 

5.72 


16-24 

10-1; 

6  16.0 

7.  09-10.  64 
3  8-10 
4-5 

16.59 

(2) 

12-15 

4.  35 


7-9 

(7.3) 


1  Approximately. 

2  No  information. 

3  Varies  with  coal.    Coal  with  28  per  cent  of  volatile  matter  used. 
«  With  H20. 

&  At  present. 
6  Variable. 
'  Trace. 


8  Trace  of  solids. 

»  Distillate,  solid. 
io  Distillate,  one-fourth  solid. 
"  Distillate,  nine-tenths  solid. 
12  Distillate,  three-fourths  solid, 
is  Distillate,  eight-ninths  solid. 
u  Distillate,  one-half  solid. 


COKE-OVEN    TARS    OF    THE    UNITED    STATES. 
produced  in  the   United  States  and  Canada. 


Examination.  Office  of  Public  Roads. 


Spe- 
cific 
gravity 
of  tar, 
25''  C. 


Per 

cent 
of  free 
car- 
bon. 


1.195 
1.206 
1. 176 
1.  168 
1.  173 


7.76 
8.77 
7.14 
0.10 
4.71 


1. 191       7. 49 


1. 169 
1.159 


1.181 
1.159 


6.56 
6.07 


8.85 
5.05 


Per 
cent 
of  ash, 


1.141       3.96 


1.  17.'. 

6.90 

1.160 

13. 94 

1.214 

14. 05 

1.143 

10.81 

1.  li.O 

1. 191 
1.  179 
1.133 

1    176 


1.171 

I    1'.'. 


I.  182 


i  211 


I    21" 


8.37 

7 

8.49 

5.21 

10.53 

u   1- 

2.  7:t 
11  30 

12,  10 

I.,    H<l 


Per 
cent 
soluble 
in  cs-2, 
includ- 
ing 
HjO. 


Distillation  results 


0.12 
.0 
.04 
.05 
.06 

.03 

.11 
.08 

.02 

.02 


.06 
.00 

.13 
.05 

.06 

.03 
.03 

.07 

.04 


92.  12 
91.16 


ss 


1.0 
1.0 


92.82     l.l 
93.85|     1.8 


93.  33 
93.85 


91.13 


P) 

6.' 
4.0 

2.0 


94.93     3.2 


93.04 
86.06 


85.82 
89.14 


92.08 
91.48 


3.3 

2.2 


.->.  4 
3.  2 


94.  72      1 .  > 
.SO.  43       1.1 


.11.-,        \7.  77      3.6 
06     i.'< 

'..7.23      : 


2  1 


U    lo  I 


(') 


5.  9 
3.  \ 


1 

2.8 


2.8 
2.0 


1.  1 
2.8 


3.0 
l.i, 
3.0 


Light  oils 
up  to 
110°  C. 


B0. 3 

.4 
1.9 
1.4 

1.0 


'2.8 

2.6 


1.7 

2.4 


-  1.  1 
2.9 

»  1.4 

1 

3.  1 

9  1.6 
1.3 
1.1 

1.  1 


9  1.7 

»  1.3 


I   s 


'".5 


0.3 
.3 
1.5 
1.2 
1.3 


2.  :< 
2.1 


1.0 

2.3 


1.2 


Middle         Heavy 

oils,  110°-!  oils,  170°- 

170°  C.  270°  C. 


5| 


0.8 
"2.0 

.7 


9.4 

.6 


... 
.6 
1.4 


9.2 

".4 


9.3 


tlUate,  two-third     "lid 
u  in  tlllate,  four-fifth     olid. 

n-ii'ii     olid. 
•,11  ii.-.  one-ninth  no  lid. 
:  illate,  "Hi-  third   "lid 

■  !<d. 

tie,  "ii>-  fifth    "hd. 


"13.  1 

9  14.0 

14.9 

"21.1 

ii  17.:. 

is  23. 6 

u  14.6 
io  17.6 

16  20.0 

18.6 


is 


Heavy 

oils,  270°- 

315°  C. 


22.8    19.5i»  13.6 
i-  16.5    II.  1    i«9.3 


.6       .5     23.5   20.4"  15.6 


11.5 
12.3 

13.2 
18.9 
15.5 

20.7 


19  8.2 

■»7.9 

a  11.9 

»5.5 

1*9.4 


7.3 

'..  9 


rial 
No. 


a.  3 


»76.6 
5*74.7 
10. 6  »  69. 5 

4. 9]^  69. 4 
8. 4*  70. 1 


9  9.8,     8.  9  "65.1 


13.0    «6.9|     5.7|26  68.4 
••a  11. 4 


1.-,.:. 
17.8 
16.3 


21  6.  5 

107.0 


.  1"  13.0    10.9 


.6       .:,     27.2 


27. 'I 

i«  12.  1 

1-  17.  2 

23.  (I 

1-21,.  It 

"IS.  1 

9  20.0 
»20.6 

i«20..r 


24.2 

24.4 

10.2 
15. 1 

21.4 

23.6 


18.0 

is.; 


•-1  9.  4 

197.3 
193.8 

19  11.0 

21  9.  6 
10  11.6 


19  12.5 

11  13.4 
9  7.1 


10.  4  »  63.  8 
:.,:  -  69.6 

6.S-  6S.0 


12.  5 

8.2 
14.4 

8.1 
6.7 

3.5 

9.7 
8.5 
10.4 

6.3 


12.0 
6.5 


57.8 

27  69.3 
-•  55.  2 

70 
"59.8 

»61.1 

»73. 
»  69.  7 
"60.8 

"63., 


Ph 


79.1  512S 

77.6  5123 
73.  i  5124 

72..".  .'.137 

73.7  5121 

68. 9  J  5125 

72. 0|  5128 

67.7  5200 

73.1  5189 

71.5  5160 

62.6  5074 

73. 2j  5081 

59.7  5095 

74.6  5083 

63  5  5159 


2«  62. 8 
28  67. 1 


64. 

77.5 
73.  2 
64 

67.6 
67.8 

66. 3 

70.2 


6.9"  72.0    74.  S 


.-.107 

5086 
5078 
5087 

5109 


5188 
5404 


5108 


..127 


-'  11.  s   10.  2-'  71. 1   75. 0  50K9 


a  Distillate,  two-fifths  Bolid 
«  Distillate,  one-seventh  solid. 
LIUate,  throe  I 

iini   tlcky. 
m  Pitch,  toi  5  Bofi  and  Btlcky. 
■    Pitch,  hard  and  brittle 
»  Pitch,  pis  itlo, 


8  COKE-OVEN    TARS   OF    THE   UNITED   STATES. 

interior  of  the  coal  block,  with  the  fire-resisting  gases  escaping  at  the 
same  time  from  the  outer  zone  of  the  block.  On  the  other  hand,  in 
the  case  of  gas  retorts,  the  heavy  vapors  escape  at  once  undiluted 
by  the  fire-resisting  gases  which  are  set  free  afterwards,  and  the 
heavy  gases  are  thus  exposed  to  the  white  heat  of  the  upper  part  of 
the  retort. " 

Answers  given  by  the  manufacturers  with  respect  to  this  question 
indicate  only  an  approximate  knowledge.  In  general  it  may  be  said 
that  carbonization  below  970°  0.  is  considered  low  temperature;  from 
970°  0.  to  1,100°  C,  medium  temperature;  and  from  1,100°  C.  to 
1,540°  C.  high  temperature;  and  that  modern  gas-house  practice 
involves  the  use  of  high  temperatures.  However  this  may  be,  it  is 
not  the  purpose  of  this  circular  to  compare  coke-oven  tars  with  gas- 
house  tars,  but  to  consider  the  former  with  relation  to  their  utility 
as  road  materials. 

From  a  total  of  31  manufacturers  to  whom  the  questions  were  sub- 
mitted 30  replies  were  received,  but  4  of  these  reported  their  plants 
as  not  in  operation.  The  remaining  26  furnished  samples  of  their 
crude  tar  for  examination  and  answered  the  questions  in  so  far  as 
they  were  able.  Upon  receipt  of  each  sample  the  entire  contents  of 
the  package  were  thoroughly  mixed  and  a  representative  sample 
taken  for  analysis.  The  results  of  these  analyses,  together  with  the 
information  furnished  by  the  manufacturers,  are  given  in  Table  I. 
In  this  table  the  different  tars  are  grouped  according  to  the  type  of 
oven  in  which  they  were  produced. 

In  columns  4  and  5  all  temperatures  are  expressed  in  degrees 
Centigrade,  although  where  the  manufacturers  gave  the  temperatures 
in  degrees  Fahrenheit  their  statements  are  shown  in  parentheses. 
In  column  5  it  will  be  noticed  that  statements  relative  to  the  maxi- 
mum temperature  to  which  the  coal  is  brought  during  distillation 
indicate  that  two  of  the  plants  run  below  970°  C,  that  a  total  of 
22  run  not  over  1,150°  C,  that  9  run  'from  950°  C.  to  1,150°  C,  and 
that  only  5  run  above  1,150°  C.  The  maximum  temperature  of 
firing  the  retorts  is,  however,  reported  in  most  cases  as  being  higher 
than  the  maximum  temperature  to  which  the  coal  is  brought. 

The  maximum  percentage  of  free  carbon  reported  is  from  16  to  24 
per  cent,  but  17  manufacturers  reported  the  maximum  percentage  of 
free  carbon  as  being  12  per  cent  or  under,  and  only  4  as  16  per  cent 
or  over. 

Analyses  of  the  samples  received  were  made  in  accordance  with  the 
methods  described  in  a  former  publication  x  of  the  office.  The  work 
consisted  in  determining  the  specific  gravity,  free  carbon,  or  organic 
matter  insoluble  in  c.  p.  carbon  disulphide  upon  a  15-minute  digestion 
at  room  temperature,  material  soluble  in  carbon  disulphide,  percent- 
age of  ash,  and  percentage  of  different  fractions  obtained  by  distilling 
a  250  c.  c.  sample  in  a  750  c.  c.  tubulated  glass  retort  with  the  ther- 

1  Bulletin  38,  Office  of  Public  Roads,  U.  S.  Department  of  Agriculture. 


COKE-OVEX    TABS   OF   THE    UNITED    STATES. 


9 


mometer  so  placed  that  the  top  of  the  bulb  was  level  with  the  bottom 
of  the  juncture  of  the  stem  and  body  of  the  retort. 

It  will  bo  noted  that  the  gravities  of  the  samples  examined  range 
from  1.133  to  1.214  and  that  the  great  majority  are  lower  than  1.200. 
This  in  itself  indicates  low  percentages  of  free  carbon.  The  mini- 
mum percentage  of  free  carbon  was  2.73,  the  maximum  16.80,  and  the 
average  for  the  20  samples  8.38.  Eighteen  samples  contained  less 
than  10  per  cent  of  free  carbon  and  8  more  than  10  per  cent.  About 
two-tbirds  of  these  products  might,  therefore,  be  considered  as  low- 
carbon  tars  and  the  otner  third  as  medium-carbon  tars.  The  amount 
of  ash  in  no  case  exceeded  0.16  per  cent,  and  in  most  cases  it  was 
practically  nil.  This  is,  of  course,  also  true  of  practically  all  gas- 
house  coal  tars.  The  percentage  oi  water  present  varied  from  a 
trace  to  10.1  per  cent  by  volume,  but  in  only  3  instances  did  it  exceed 
5  per  cent.  Water  is  a  variable,  depending  upon  a  number  of  condi- 
tions, and,  as  it  is  not  a  pail  of  the  true  tar,  has  been  eliminated 
in  Table  II.  Before  leaving  Table  I,  however,  it  is  of  interest  to  note 
that  14  of  the  pitch  residues,  remaining  after  distillation  had  been 
carried  to  315°  ('.,  were  either  soft  or  plastic — a  condition  which  has 
seldom  been  noticed  by  the  author  in  the  distillation  of  gas-house 
eoal  tars.  The  amount  of  solids  which  crystallized  or  precipitated 
out  of  the  different  fractions  was  found  to  vary  greatly,  as  shown 
in  i he  foot-notes  to  Table  I. 

Table   II.     Analysis  of  coke-oven  tars  upon  a  mater-free  basis. 


Type  of  oven. 

Percent- 
age of 

free  car- 
bon. 

Fractions  1>>  weigh  I. 

num- 
ber. 

Percent- 
age up 
toll0°C 

Percent- 
age from 
1 10-1 70°  C. 

Percent- 
age from 

Percent- 
age from 
270-315°C. 

Percent- 
age of 

pitch. 

51 20 
5123 

Semet-Sol  v:i\ : 

do 

7.82 

8.84 
7.21 
6.19 
4.73 
7.49 
6.97 

9.00 
5. 19 
4.04 
7.09 
14.22 

11.12 

8.  02 

8.60 

[o.ea 

12.56 
3.96 
2.81 

11.51 

ia  62 

17.  17 

0.30 

.30 

1. 55 

1.21 

1.30 

.30 

2.44 

2. 1 " 

1.42 

1.95 

1.32 

1.02 

2.  34 

1.40 

1 .  .VI 

2.57 

1.2! 

.91 

.91 

.'HI 

1 .  34 
1.21 
1.03 
1.43 

2,  50 
.3«> 

0.70 
1.71 
.00 
.00 
.00 
.90 
.31 
.51 
.20 
.  30 
.81 
.-'ii 
.51 

.  10 

.51 

.01 

.-in 
.-ii) 

1.31 
.  HI 
M0 
.20 
.30 
.50 
23 

L73 

11.59 
12. 39 
13.33 
19.18 
15. 57 
20.  70 
13.81 
tl  hi 
18.  in 
16.76 
19.89 
14.50 
20,  si 
11.40 
24.  89 
25. 15 
L0.30 
16.29 
21  63 
23.  83 
16.89 
18  29 
19.07 
18.66 
6.  66 

10.  12 

7.35 
0.95 

10.70 
1. 97 
8.44 
8.90 
B  06 

10.76 
5.79 
6,99 

1 2.  75 
8.  13 

i  i  69 
V47 

8.60 

9.79 

8.1,1 

10.51 
6.86 

11.41 

12  19 

7.M 

79.  73 
7s.  22 

5-24 

...do 

5137 

...do 

73.  60 

5121 

do 

74.07 

51 -'.5 

do 

5128 

...do 

76.  a 

5200 
5180 

do 

do 

70. 08 
74.36 

5100 

do 

73.  55 

.5074 

.do 

1  :■;.  B7 

.do 

75.30 

5095 

do.                

78.08 

do 

66.  32 

.",107 

do 

66.  90 

MM., 

78.  28 

do 

71.  16 

5087 

...do 

65.  n 

5100 

do. 

do 

69.  89 

67.87 

72.  37 

5127 

Otto  Hodman  and  United  Otto 

do 

71.  r, 
81.67 

5088 

i  nlted  Otto  and  Rothber] 

The  results  given  m  Table   II   arc  calculated   upon  a   water-free 

basfe       i.e.,   the  percentages   are   expressed    in    terms  of  the   actual   tar 

exclusive  of  water.     Considering  these  products  according  to  type, 


10 


COKE-OVEN    TABS   OF   THE   UNITED   STATES. 


it  will  be  seen  that  the  tar  produced  by  the  Koppers  ovens  contains 
the  lowest  percentage  of  free  carbon,  the  Semet-Solvay  tars  the 
next  lowest,  the  United  Otto  next,  the  Otto  Hoffman  next,  and 
the  mixed  tar  from  the  United  Otto  and  Rothberg  ovens  contains 
the  highest  percentage  of  free  carbon.  For  the  sake  of  comparison 
the  minimum,  maximum,  and  average  percentages  of  free  carbon 
for  eiich  of  these  types  are  shown  in  Table  III. 

Table  III. — Percentage  of  free  carbon  in  coke-oven  tars. 
(Water-free  basis.] 


Type  of  oven. 


Percentage  of  free  carbon. 


Minimum.   Maximum.     Average 


Koppers 

Semet-Solvay 

United  Otto 

Otto  Hoffman 

Otto  Hoffman  and  United  Otto  (mixed) 
United  Otto  and  Rothberg  (mixed). . .. 


2.81 
4.04 
5.20 
8. 02 
11.51 
17.17 


3.95 
9.00 
12.55 
14.09 
13.52 
17.17 


3.38 
6.74 
9.00 
12.10 
12.51 
17.17 


The  percentages  of  various  fractions  for  the  different  types  of 
tars  overlap  to  such  an  extent  that  no  detailed  comparison  will 
be  made.  The  maximum,  minimum,  and  average  total  distillates 
to  315°  C.  for  the  different  types  are,  however,  given  in  Table  IV. 

Table  IV. — Percentage  by  volume  of  total  distillate  to  315°  C.  in  coke-oven  tars. 

[Water-free  basis.] 


Type  of  oven. 


Percentage  by  volume. 


Minimum.    Maximum.     Average 


(Coppers 

Semet-Solvay 

United  Otto 

Otto  Hoffman 

Otto  Hoffman  and  United  Otto  (mixed) 
United  Otto  and  Rothberg  (mixed) .... 


30.5 
22.0 
25.0 
25. 3 
19.9 
26. 9 


30.0 
40.8 
38.5 
43.0 
32.1 
20.9 


33.3 
29.9 
32.6 
30.0 
20. 0 
20.9 


From  this  Table  it  is  evident  that  wide  variations  exist  in  the 
relation  of  total  distillate  to  pitch  residue  in  the  coke-oven  tars 
produced  in  this  country,  and  this  is  even  true  of  different  tars 
produced  by  the  same  type  of  oven. 

Straight  coal-tar  road  binders  or  refined  coal  tars  are  usually 
manufactured  by  subjecting  the  crude  material  to  a  process  of  dis- 
tillation with  or  without  steam  or  air  agitation.  Distillation  is 
carried  to  the  point  at  which  the  residuum  remaining  in  the  still  has 
obtained  the  desired  consistency  at  normal  temperatures,  and  this 
involves  the  removal  of  certain  of  the  more  volatile  oils  present  in 
the  crude  material.  For  use  in  construction  work  a  soft  and  almost 
fluid  pitch  is  often  produced,  and  the  consistency  of  this  pitch  is 


COKE-OVEN    TABS    OF    THE    UNITED    STATES.  11 

controlled  by  means  of  a  melting  point  or  float  test.  When  the 
crude  tar  runs  abnormally  high  in  free  carbon,  it  is  sometimes  mixed 
with  crude  water-gas  tar  before  distillation.  Water-gas  tar  con- 
tains a  very  low  percentage  of  free  carbon,  and  by  properly  propor- 
tioning the  two  a  product  is  obtained,  upon  distillation,  which 
does  not  carry  more  than  the  maximum  limit  of  free  carbon  set  by 
manufacturers.  What  the  maximum  limit  should  be  is  a  much 
mooted  question  among  those  who  have  given  thought  to  this  mat- 
ter. The  governing  considerations  are:  (1)  What  is  the  most  econom- 
ical limit  from  the  standpoint  of  manufacture?  and  (2)  What  is 
the  proper  limit  with  regard  to  the  utilization  of  the  product  as  a 
road  material?  For  a  number  of  reasons,  which  it  is  unnecessary 
to  mention  in  this  circular,  an  excessively  high-carbon  tar  is  difficult 
to  distill  properly  and,  with  other  things  equal,  the  lower  the  per- 
centage of  carbon  the  easier  and  shorter  the  distilling  process.  From 
this  standpoint,  therefore,  by-product  coke-oven  tars  are  well  adapted 
to  the  manufacture1  of  road  binders.  Moreover,  because  of  their 
low  percentage  of  free  carbon,  they  may  be  employed  in  a  manner 
similar  to  water-gas  tars,  when  it  is  desired  to  utilize  a  crude  high- 
carbon  tar  in  the  production  of  a  medium-carbon  tar  road   binder. 

In  an  ordinary  road  tar  for  use  in  construction  work  where  free 
carbon  is  present  to  the  extent  of  about  20  per  cent,  the  proportion 
of  total  distillate,  below  315°  C,  to  pitch  residue  is  approximately 
1  to  4.  Where  this  relation  exists  the  pitch  residue  is  hard  and 
brittle.  A  residue  which  is  soft  or  plastic  is  to  be  preferred,  as 
it  would  indicate  longer  life  during  service,  and  where  such  a  residue 
is  present  the  proportion  of  distillate  would  naturally  be  lower 
for  a  given  consistency,  as  the  distillates  may  be  considered  as 
fluxes  for  the  residues.  If  such  is  the  case,  it  is  evident  from  the 
foregoing  tables  that  coke-oven  tars  oiler  a  valuable  source  of  supply 
for  tar  road  binders.  As  an  example,  even  the  highest -carbon 
tar,  No.  5089,  if  distilled  to  the  point  where  the  proportion  of  dis- 
tillate, below  315  <'.,  to  the  pitch  residue  was  as  1  to  4,  would  con- 
tain less  than  l'.t  per  cent  of  free  carhoii.  which  is  at  present  con- 
sidered as  not   excessive  for  a  refined  coal  tar. 

In  conclusion  it  may  he  said  that  indications  point  strongly  to 
the  fact  that  by-product  coke  ovens  will  eventually  play  a  most 
important  part  in  the  road-mat  dial  industry,  and  it  is  to  be  hoped 
that  their  general  adoption  in  this  country  will  be  rapid.  The 
future  demand  for  economical  bituminous  road  hinders  in  the  I  oited 
States  will  undoubtedly  exceed  the  supply,  and  this  in  spile  of  the 
natural  increase  in  petroleum  and  asphalt  road  binders.  If  such 
is    the    case,    the    present    loss   of   enormous   quantities   of   tar.    to   sa\ 

Dothing  of  gas  and  ammonia,  because  of  the  use  of  beehive  ovens, 

is  a  matter  Worth)  of  the  utmost  consideration  oil  the  part  of  all 
who  arc  interested    in   the  conservation   of  our  resources. 

o 


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